Collapsible firearm butt-stock assembly

ABSTRACT

A collapsible firearm butt-stock assembly has a shoulder stock 18 coupled with a pair of guide rods 20, 22 slideable in respective guide holes 14, 16 of a housing 12. A locking mechanism including locking members engageable with guide rod recesses 26, 28 provided in the guide rods has an actuator 30 that is movable in the lengthways direction of the guide rods to release the locking members to allow sliding movement of the shoulder stock relative to the housing.

I. CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.K. patent application no. GB2207069.2 filed on May 13, 2022.

II. FIELD OF USE

The invention relates to collapsible firearm butt-stock assemblies.

III. DESCRIPTION OF THE RELATED ART

The AR15/M16/M4 series of firearms is popular due to their customisable design, which allows the construction and accessorising of the firearm for specific applications. There are many manufacturers producing and selling aftermarket components for customising AR15/M16/M4 firearms

There is a desire amongst many individual users and user bodies to have the option of selectively reducing the size of the AR15/M16/M4 firearm so that it is easier to carry or store. This is achievable by the use of collapsible butt-stock assemblies.

Examples of collapsible firearm butt-stock assemblies are disclosed by US9541347 and US9915497. The collapsible butt-stock assembly disclosed by US9541347 has a locking mechanism that is operable to lock the shoulder stock in a plurality of extended positions relative to a buffer tube housing that is secured to the rear end of the receiver of the firearm. The locking mechanism is mounted on the shoulder stock. US9915497 discloses a similar collapsible butt-stock assembly, but with the locking mechanism mounted on the buffer tube housing. In each case the locking mechanism is released by pressing a release member mounted on a side of the buffer tube housing/shoulder stock in a direction that is perpendicular to the lengthways direction of the butt-stock assembly, which is also perpendicular to the longitudinal axis of the firearm.

It is an object of the invention to provide a collapsible firearm butt-stock assembly that is an improvement on existing collapsible firearm butt-stock assemblies, or at least, an alternative to existing products that are on the market.

SUMMARY OF THE INVENTION

The invention provides a collapsible firearm butt-stock assembly as specified in claim 1.

The invention also includes a collapsible firearm butt-stock assembly as specified in claim 15.

The invention also includes a firearm as specified in claim 14.

The invention also includes a method of adjusting a collapsed/extended condition of a collapsible firearm butt-stock assembly as specified in claim 17.

BRIEF DESCRIPTION OF THE DRAWINGS

In the disclosure that follows, reference will be made to the drawings in which:

FIG. 1 is a perspective view of a collapsible firearm butt-stock assembly;

FIG. 2 is a section on the longitudinal axis of the butt-stock assembly;

FIG. 3 is a side view the firearm butt-stock assembly shown in FIGS. 1 and 2 in an extended locked condition;

FIG. 4 is a section view on line IV-IV in FIG. 3 ;

FIG. 5 is an enlargement of portion A of FIG. 4 ;

FIG. 6 is a side view corresponding to FIG. 3 showing the firearm buttstock assembly in an unlocked extended condition;

FIG. 7 is a section on line VII-VII in FIG. 6 ;

FIG. 8 is an enlargement of portion B in FIG. 7 ;

FIG. 9 is a schematic side view of the firearm butt-stock assembly of FIGS. 1 to 8 fitted to a firearm and in a fully collapsed condition;

FIG. 10 is a view corresponding to FIG. 9 showing the firearm butt-stock assembly in a fully extended condition;

FIG. 11 is a partially sectioned top view of a modified collapsible firearm butt-stock assembly;

FIG. 12 is an enlargement of portion C in FIG. 11 ; and

FIG. 13 is an enlargement of a portion of FIG. 12 .

DETAILED DESCRIPTION

In the description that follows, use of the terms front, rear, forwards, rearwards, foremost, rearmost, leading and trailing ends is made with reference to the conventional orientation of a firearm in which the muzzle represents the front, or leading, end and the shoulder stock the rear, or trailing, end of the firearm.

Referring to FIGS. 1 to 5 , a collapsible firearm butt-stock assembly 10 comprises a housing 12 defining first guide hole 14, a second guide hole 16 and a shoulder stock 18. The firearm butt-stock assembly further comprises a first guide rod 20 inserted in the first guide hole 14 and a second guide rod 22 inserted in the second guide hole 16. The first and second guide rods 20, 22 are configured so as to be able slide back and forth in the respective guide holes 14, 16 to allow movement of the shoulder stock 18 relative to the housing 12. The firearm butt-stock assembly 10 further comprises a locking mechanism 24 releasably engageable with at least one first guide rod recess 26 defined by the first guide rod 20 and at least one second guide rod recess 28 defined by the second guide rod 22 to limit movement of the shoulder stock 18 relative to the housing 12. The locking mechanism 24 comprises a user operable actuator 30 that is movable in a first direction, that is away from the shoulder stock 18, to release the locking mechanism from engagement with the first and second guide rod recesses 26, 28 to allow the guide rods 20, 22 to slide in the respective guide holes 14, 16 so that the shoulder stock 18 can move relative to the housing 12. The actuator 30 is also movable in a second direction, that is opposite the first direction, to cause the locking mechanism 24 to engage the at least one first guide rod recess 26 and the at least one second guide recess 28 to lock shoulder stock 18 in position, or at least substantially prevent movement of the shoulder stock 18 relative to the housing 12. In the embodiment illustrated by FIGS. 1 to 8 , there are five first guide rod recesses 26 and five second guide rod recesses 28 arranged in pairs disposed in facing relationship. The guide rod recesses 26, 28 are elongate slots extending perpendicular to the longitudinal axis of the respective guide rods. The guide rod recesses 26, 28 have a hemispherical cross-section.

In the embodiment illustrated by FIGS. 1 to 8 , the housing 12 comprises a through-bore 32 that houses a buffer tube 34. The buffer tube 34 has a leading, or front, end provided with threading 36 configured to be screwed into complementary threading provided in the rear end of a receiver 38 of a firearm 40 (see FIGS. 9 and 10 ). As shown in FIG. 2 , the buffer tube 34 may be a two-piece assembly comprising a rear end portion 34R having an enlarged leading, or front, end 42 that is provided with internal threading 41 and a front-end portion 34F that has the threading 36 at its leading, or front end, and similar external threading 43 at its rear end that is complementarily engageable with the internal threading in the front end 42 or the rear end portion.

The leading end of the housing 12 is provided with one or more protrusions 42 that are configured to engage in a recess or recesses provided in the rear end of the receiver 38 so that the housing 12 is prevented from twisting relative to the receiver once the threading 36 has been screwed into the threading provided in the receiver. Thus, the housing 12 can be rigidly fixed to a receiver 38 of a firearm 40. The firearm 40 may, for example, be an autoloading firearm in the AR15/M16/M4 series of firearms. This series of firearms will be well known to those skilled in the art and so the fitting of the buffer tube 34 to and construction of such a receiver will not be given here.

Although not essential, in embodiments that are configured for fitting to a firearm in the AR15/M16/M4 series of firearms, the through-bore 32 has a longitudinal axis that extends parallel to the respective longitudinal axes of the first and second guide holes 14, 16 and is disposed in a first plane that is separate from and above a second plane in which the longitudinal axes of the first and second guides holes 14, 16 are disposed. Again, although not essential, for embodiments configured for fitting to a firearm in the AR15/M16/M4 series of firearms, the upper portion 48 of the housing 12 (as viewed in FIG. 1 ) may be relieved on each side to form a cheek pad or comb. Preferably, the relieving of the upper portion 48 to form the cheek pad or comb may take the form of respective chamfered surfaces 50. As an alternative to chamfers as shown in FIG. 1 , the surface 50 may comprise respective outwardly curved surfaces so that in cross-section, the upper portion 48 resembles an arch, which may have a flat top. The lower portion 50 of the housing 12 in which the first and second guide rods 20, 22 are housed is wider than the upper portion 48 and the configuration is such that the housing 12 has a generally bell-shaped cross-section with the through-bore 32 located centrally above the first and second guide holes 14, 16. This arrangement enables the first and second guide rods 20, 22 to extend past a lower part of the receiver of an AR15/M16/M4 series firearm when the shoulder stock 18 is moved back and forth relative to the housing 12.

Referring to FIGS. 4 and 5 , the actuator 30 is housed in a blind bore 54 provided in the trailing, or rear, end of the housing 12. The blind bore 54 has a longitudinal axis that extends parallel to the respective longitudinal axes of the first and second guide holes 14, 16 and the through-bore 32 and is preferably disposed in the same plane as the longitudinal axes of the first and second guide holes 14, 16. The blind bore 54 is sized such that the actuator 30 can move in the first and second directions guided by the longitudinally extending sidewall of the blind bore. A resilient biaser 56 is provided between the inner end 58 of the actuator 30 and an end wall 60 formed by the inner end of the blind bore 54. Although not essential, the resilient biaser 56 may take the form of a compression spring as shown in the drawings. In other embodiments, the resilient biaser 56 may take the form of a resilient pad disposed between the inner end 58 and end wall 60. In embodiments in which the resilient biaser 56 takes the form of a compression spring, a bore 62 may be provided in the inner end 58 of the actuator 30 to receive an end of the compression spring and a projection (not shown) may be provided on the end wall 60 to locate the compression spring between the actuator and the end wall 60. Alternatively, a compression spring may be located by respective projections provided on the inner end 58 of the actuator 30 and the end wall 60.

The actuator 30 comprises a cylindrical actuator body 64 that is provided with recessing to receive first and second locking members, which in the illustrated embodiment are rolling elements in the form of first and second balls 66, 68. Although not essential, the recessing may take the form of a slot 70 extending around the circumference of the actuator body 64 to receive the first and the second balls 66, 68. The first and second balls 64, 66 are housed in respective transverse bores 72, 74 that extend from the blind bore 54 to the outer periphery of the actuator body 64 so that the first and second balls 66, 68 are trapped between the actuator body 64 and the first and second guide rods 20, 22 respectively. The transverse bores 72, 74 preferably have a diameter slightly greater than the diameter of the first and second balls 66, 68 so that the balls are guided by the bores for radial movement generally perpendicular to the longitudinal axis of the actuator body 64.

The actuator 30 is provided with an inclined face 76 that faces the shoulder stock 18 and is configured to drive the balls 66, 68 in a radially outwards direction with respect to the longitudinal axis of the actuator when the actuator moves in the second direction. Thus, when the actuator 30 moves towards the shoulder stock 18, the balls 64, 66 are automatically caused to move in a radially outwards direction. In the embodiment shown in the drawings, the inclined face 76 is the sidewall of the circumferentially extending slot 70 that disposed closest to the leading end of the actuator body 64 and facing the shoulder stock 18. The inclined face 76 extends radially outwardly and axially towards the inner end 58 of the actuator 30 from a radially innermost end at the base of the slot 70 to the outer periphery of the actuator.

The blind bore 54 extends into the housing 12 from an open end formed in a rear end face of the housing 12 that faces the shoulder stock 18. Although not essential, the trailing, or rear, end of the actuator body 64 may be provided with a reduced diameter portion defining a button 80 that projects from the housing 12, at least when the locking mechanism 24 is acting to limit movement of the shoulder stock 18 relative to the housing 12. It is to be understood that it is not essential that the actuator 30 projects from the housing 12 and all that is necessary is that it a user can engage with it to move it sufficiently far to release the balls 66, 68 so that the balls can disengage the first and second guide rod recesses 26, 28. Thus, for example, provided the actuator 30 is sufficiently wide or sufficient relief is provided at the open end of the blind bore 54 to allow user access to the actuator 30, the actuator may be entirely contained within the housing 12 under all operating conditions.

Referring to FIG. 1 , the shoulder stock 18 is provided with a hole 84 configured to receive the buffer tube 34. The hole 84 may be a through-hole or a blind hole according to the particular configuration of the shoulder stock 18 and buffer tube 34 and the extent to which the butt-stock assembly 10 is to be collapsed. In the illustrated example, the hole 84 is a through-hole. The shoulder stock 18 is provided with respective through-holes 86, 88 to receive the trailing, or rear, ends of the first and second guide rods 20, 22. As best seen in FIG. 1 , the layout of the holes 84-88 corresponds to the layout of the first and second guide holes 14, 16 and through-bore 32. Although not essential, the upper portion of the shoulder stock 18 may be profiled such that its cross-section shape at least substantially corresponds to the cross-section shape of the housing 12.

The ends of the guide rods 20, 22 and the though-holes 86, 88 may be provided with respective complementarily engageable flat surfaces 90, 91. Similarly, respective complementarily engageable shoulders 92, 93 are provided on the guide rods 20, 22 and in the through-holes 86, 88. The configuration of the flat surfaces 90, 91 and shoulders 92, 93 is such that when the first and second guide rods 20, 22 are fully inserted into the through-holes 86, 88, the guides rods are correctly positioned so that the first and second guide rod recesses 26, 28 are disposed in opposed spaced apart pairs that are correctly orientated so as to be engageable by the first and second balls 66, 68.

The ends 94, 95 of the through-holes 86, 88 at the rear end face 99 of the shoulder stock 18 are configured to receive respective fixing screws (not shown). The ends of the first and second guide rods 20, 22 housed in the through-holes 86, 88 are provided with a threaded hole 96, 98 by means of which screws inserted into the ends 94, 95 of the through-holes 86, 88 are used to secure the first and second guide rods 20, 22 to the shoulder stock 18.

The shoulder stock 18 may be manufactured from aluminium, an engineering polymer or other suitable metals. The rear end face 99 of the shoulder stock 18 may be textured so as to provide a nonslip surface.

In use, the shoulder stock 18 may be moved between a fully extended locked position and a fully collapsed locked position and a range of extended locked positions intermediate the collapsed and extended locked positions, such as the extended locked position shown in FIGS. 3 to 5 . These positions are defined by the engagement of the locking mechanism 24 with the first and second guide rod recesses 26, 28. In the illustrated embodiment, there are five pairs of first and second guide rod recesses defining five locked positions, although, in other embodiments, there may be a greater or less number as required. For example, in a simple embodiment, there may just be a collapsed locked position and a fully extended locked position. Although not essential, in the illustrated embodiment when in the fully collapsed locked position, the shoulder stock 18 is disposed adjacent to, or abutting, the front end 42 of the rear end portion of the buffer tube 34 so that the butt-stock assembly 10 has a minimal length, thereby reducing the overall length of the firearm to which it is fitted.

Starting from the extended locked position shown in FIG. 3 , if the user wishes to collapse or compress the butt-stock assembly 10, the button 80 is pressed to move the actuator body 64 away from the shoulder stock 18 and into the blind bore 54. Once the actuator body 64 is pushed sufficiently far into the blind bore 54, the first and second balls 66, 68 are released and free to move radially inwardly in the transverse holes 72, 74 in response to pressure applied by the initiation of movement of the shoulder stock 18 so that their radially inner end regions are received in the circumferentially extending slot 70 of the actuator body 64 as shown in FIGS. 7 and 8 . Thus, operation of the actuator 30 by the user allows the first and second balls 66, 68 to move out of engagement with the first and second guide rod recesses 26, 28 (as shown in FIGS. 4 and 5 ) to a position in which they are wholly disposed within the housing 12 or at least protrude from it to the extent that they do not engage in the first and second guide recesses 26, 28 so that the first and second guide rods 20, 22 are free to slide in the first and second guide holes 14, 16. Accordingly, the shoulder stock 18 can be moved towards the housing 12 to commence collapsing of the collapsible firearm butt-stock assembly 10, as can be seen by comparing FIGS. 4 and 5 . Starting from the position shown in FIG. 4 , the shoulder stock 18 can be moved forwards towards the housing until the transverse bores 70, 72 are roughly aligned with a pair of first and second guide recesses 26, 28 disposed rearwardly of the first and second guide recesses the balls 66, 68 are shown engaging in FIG. 4 and the actuator 30 then released. For example, the shoulder stock 18 could be moved forwards towards the housing 12 until the transverse bores 70, 72 are generally aligned with the rearmost pair of first and second guide recesses 26, 28 to fully collapse the butt-stock assembly 18. When the actuator 30 is released, the energy stored in the resilient biaser 56 is released causing the actuator to be towards the shoulder stock 18. As the actuator 30 moves in the blind bore 54 towards the shoulder stock 18, the inclined face 76 of the slot 70 acts in the manner of a cam causing the first and second balls 66, 68 to move progressively radially outwardly in the direction of the first and second guide rods 20, 22 until the balls engage in the respective first and second guide rod recesses 26, 28 to lock the shoulder stock 18 in position, thereby limiting movement of the shoulder stock 18 relative to the housing 12.

It will be understood that starting from the position shown in FIG. 4 , instead of moving the shoulder stock 18 towards the housing 12 to collapse the butt-stock assembly 10, the user could move the shoulder stock 18 away from housing 12 to further extend the butt-stock assembly. From the position shown in FIG. 4 , there are two pairs of first and second guide rod recesses 26, 28 defining two further extended conditions of the butt-stock assembly 10, including the foremost pair, which corresponds to the fully extended locked condition of the butt-stock assembly 10.

It will also be understood that it is no necessary for the user to continuously press the actuator 30 into the blind bore 54 while the shoulder stock 18 is being moved towards or away from the housing 12. For example, the actuator 30 may be released ahead of the arrival of the first and second balls 66, 68 at the location of the pair of first and second guide recesses 26, 28 corresponding to the desired collapsed/extended state of the butt-stock assembly 10. In that case, the first and second balls 66, 68 will be forced radially outwardly with respective to the actuator 30 into engagement with the first and second guide rods 20, 22 and will roll along the opposing surfaces of the guide rods until they simply ‘pop out’ into engagement with the selected pair of first and second guide recesses 26, 28 as they move into alignment with them. In some embodiments, the first and second guide rods 20, 22 may be provided with a flat track 22F (FIG. 2 ) running between the first and second guide rod recesses 26, 28. The respective flat tracks 22F are dispose opposed parallel spaced apart relationship and are orientated perpendicular to the longitudinal axes of the first and second guide rods 20, 22 Also, provided sufficient momentum is maintained once the actuator 30 has been initially operated to release the locking mechanism 24 from engagement with a pair of first and second rod recesses 26, 28 with which it is engaged, it is in principle possible to move the shoulder stock 18 back and forth at will until a desired collapsed/extended position is attained without having to further operate the actuator.

Referring to FIGS. 9 and 10 , the collapsible firearm butt-stock assembly 10 is shown fitted to the rear end of the receiver 38 of a firearm 40. The firearm 40 may be one of the AR15/M16/M4 series of firearms. In FIG. 9 , the butt-stock assembly 10 is shown in a fully collapsed condition in which the shoulder stock 18 abuts the front end 42 of the rear portion of the buffer tube 34 and is close to the housing 12. It will be understood that in embodiments with a different configuration of the buffer tube 34, the shoulder stock 18 may abut or be separated from the housing 12 by a small clearance when the butt-stock assembly 10 is in a fully collapsed condition.

In FIG. 10 , the collapsible firearm butt-stock assembly 10 is shown in a fully extended condition in which the shoulder stock 18 is disposed remote from the housing 12 by the furthest amount permitted by the configuration of the first and second guide rods 20, 22 and first and second guide rod recesses 26, 28 corresponding to engagement of the first and second balls 66, 68 in the foremost first and second guide rod recesses 26, 28, as shown in FIGS. 4 and 7 .

FIGS. 11 to 13 show a modified collapsible firearm butt-stock assembly 110. Parts of the butt-stock assembly 110 the same as or similar to parts of the butt-stock assembly 10 are indicated by the same reference numerals incremented by 100 and may not be described in detail again. The difference between the butt-stock assembly 110 and the butt-stock assembly 10 is that rearmost pair of first and second guide rod recesses 126R, 128R, corresponding to the fully collapsed condition of the butt-stock assembly shown in FIG. 11 , are relieved on their forward sides. Thus, instead of having a symmetrical cross-section and being at least substantially hemi-spherical, the first and second guide rod recesses 126R, 128R are relieved in the direction of the longitudinal axes of the first and second guide rods 120, 122 towards the front end of the guide rods, so that the first and second guide rod recesses 126R, 128R have an asymmetric cross-section. By, relieving, or opening out, the forward sides of the first and second guide rod recesses 126R, 128R to provide respective inclined surfaces, the resistance of the locking mechanism to movement of the shoulder stock 118 away from the housing 112 is reduced to the extent that when in a position corresponding to the fully collapsed condition of the butt-stock assembly 110 shown in FIGS. 11 to 13 , movement of the shoulder stock away from the housing can be initiated without operating the actuator 130 and provided sufficient momentum is maintained, the shoulder stock can be moved relative to the housing until the required position is reached without having to operate the actuator 130. Thus, in embodiments using the modification illustrated by FIGS. 11 to 13 , it is possible for a user to adjust the position of the shoulder stock 118 from the fully collapsed condition to a selected extended condition without having to move the actuator 130 to release the locking mechanism.

In the illustrated embodiments, the first and second guide rods are each provided with five guide rod recesses, which define a fully extended condition, a fully collapsed condition and three intermediate collapsed/extended conditions. This is not to be taken as limiting and the number of guide rod recesses may be selected to provide a greater or lesser number of collapsed/extended conditions as desired. Indeed, the advantageous features of the butt-stock assembly may apply even when there is only one pair of guide rod recesses corresponding to a fully extended condition of the shoulder stock. In this connection, the skilled person will appreciate that while locking of the shoulder stock in the fully extended and intermediate extended condition is needed, for some applications it may be sufficient that the shoulder stock can be moved to a fully collapsed condition in which it may be maintained by friction between the locking mechanism and the guide rods.

In the illustrated embodiments, the locking members of the locking mechanism are rolling elements in the form of respective balls. It is to be understood that while the ease with which balls can be caused to move radially with respect to the actuator and past the opposed faces of the guides rods makes the user of balls, the use of balls as locking members is not essential. For example, in some embodiments the locking members may comprise cylindrical rods having a hemispherical guide rod engaging end and an inclined face that at least substantially complements an inclined surface of the actuator body may be used to provide locking members that move radially with respect to the actuator for engaging and disengaging respective guide rod recesses.

A feature of collapsible firearm butt-stock assemblies according to the invention is the ease with which the shoulder stock may be moved relative to the housing. The locking mechanisms of the butt-stock assemblies disclosed by US9541347 and US9915497 have actuators that are operated from a side of the butt-stock assembly, which means that they are handed. Because the actuator in a butt-stock assembly according to the invention is moved in the lengthways direction of the butt-stock assembly, it can be configured so that it is not handed. In other words, a lefthanded or righthanded user can readily operate the actuator using their dominant hand, which is not the case with locking mechanisms disclosed by US9541347 and US9915497. Furthermore, in the case of a butt-stock assembly with the locking mechanism actuator mounted on the shoulder stock as disclosed by US9541347, it is not possible for a user holding the pistol grip 100 (FIGS. 9 and 10 ) to reach the actuator with the same hand. Even if the actuator is mounted closer to the pistol grip as in the butt-stock assembly disclosed by US9915497 so that with the correct design the actuator could be reached by a thumb of a hand holding the pistol grip, pushing the actuator in a direction transverse to the lengthways of the butt-stock assembly is a difficult and would result in an unstable action causing a tipping of the firearm and a potential loosening of the user’s grip on the firearm. In the case of a butt-stock assembly in which the actuator is moves in the lengthways direction of the butt-stock assembly, the configuration may be such that the user can readily operate the actuator with the thumb of a hand holding the pistol grip and the natural consequence of the squeezing action produced is a firmer grip on the firearm and stable operation. By a suitable selection of the configuration of the butt-stock assembly, it can be made possible for the thumb of a hand gripping the pistol grip 100 with the trigger finger inserted in the trigger guard 102. Thus, ambidextrous one-handed operation of the butt-stock assembly, and in particular release of the locking mechanism and adjustment of the collapsed/extended condition of the butt-stock assembly, is facilitated in a way not possible with the butt-stock assemblies disclosed by US9541347 and US9915497.

In the illustrated embodiments, the actuator is housed in a housing that houses a buffer tube and through which respective guide holes for guide rods coupled to the shoulder stock extend. In some embodiments, the housing and buffer tube are particularly configured for fitting to a firearm of the AR15/M16/M4 series of firearms. It is to be understood that this is not essential. In other embodiments, the housing for the actuator may be an integral part of the firearm. Furthermore, the guide holes for the guide rods may be defined by suitably configured bodies secured to the housing so that respective guide holes are defined between the housing and the bodies and the housing.

In the illustrated embodiments, there are respective locking members for releasably engaging respective sets of guide rod recesses defined by the first and second guide rod members. It is to be understood that while having the locking mechanism releasably engage guide rod recesses advantageously provides secure and stable locking of the shoulder stock in its extended position or positions, this is not essential. In currently non-preferred embodiments, a first locking member may engage at least one guide rod recess defined by one guide rod, a second locking member merely engages a surface of the other guide rod. While this configuration may not provide such secure locking as the illustrated embodiments, it should still provide stable locking that prevents twisting of the shoulder stock relatively to the housing or firearm. The above-described advantages of improved user operability may also be obtained in currently non-preferred embodiments in which the locking mechanism has only one locking member releasably engageable with one of the guide rods and the locking mechanism does not interact with the other guide rod.

In the illustrated embodiments, the guide rod recesses are disposed in pairs in opposed spaced apart relationship. This is advantageous as it allows the first and second locking members to be releasable into a common slot provided in the actuator. However, it is not essential. Although not currently preferred, in some embodiments, the first and second guide rods may be staggered and the first and second locking members corresponding staggered with respective recessing being provided in the actuator. It will also be appreciated that even when the first and locking members are aligned as in the illustrated embodiments, the actuator may be provided with separate recesses to receive the locking members when they are disengaged from the guide rod recesses. However, this would require that the actuator is mounted in the housing in a particular orientation.

It will be understood that when the shoulder stock 18 is positioned intermediate its fully collapsed position and its fully extended position, it may be considered to be in partially extended or partially extended position and correspondingly, the collapsible firearm butt-stock assembly may be considered to be in a partially extended or partially collapsed condition in this context, the terms collapsed and extended are used interchangeably herein. 

I claim:
 1. A collapsible firearm butt-stock assembly comprising: a housing provided with a first guide hole and a second guide hole; a shoulder stock coupled to a first guide rod that is inserted in said first guide hole and a second guide rod that is inserted in said second guide hole, the guides rods being configured so as to be able to slide in the respective guide holes to allow movement of said shoulder stock relative to said housing; and a locking mechanism comprising at least one locking member releasably engageable with at least one guide rod recess defined by said guide rods to limit said movement of the shoulder stock relative to said housing, and a user operable actuator that is movable in i) a first direction that is away from said shoulder stock to release said at least one locking member from engagement with said at least one guide rod recess to allow said guide rods to slide in said guide holes so that said shoulder stock can move relative to said housing and ii) a second direction that is towards said shoulder stock to cause said at least one locking member to engage said at least one guide rod recess.
 2. The collapsible firearm butt-stock assembly claimed in claim 1, wherein said actuator is mounted in a bore provided in said housing, said bore having an open end facing said shoulder stock and configured to enable said user to operate said actuator.
 3. The collapsible firearm butt-stock assembly claimed in claim 2, further comprising a resilient biaser disposed in said bore to bias said actuator in said second direction.
 4. The collapsible firearm butt-stock assembly claimed in claim 1, wherein said housing has a face that faces said shoulder stock, said bore extends into said housing from said face and said actuator has an end that protrudes from said face when said at least one locking member is in releasable engagement with said at least one guide rod recess.
 5. The collapsible firearm butt-stock assembly claimed in claim 1, wherein said first guide rod is provided with at least one first guide rod recess and said second guide rod is provided with at least one second guide rod recess and said locking mechanism comprises a first said locking member that is releasably engageable with said at least one first guide rod recess and a second locking member that is releasably engageable with said at least one second guide rod recess.
 6. The collapsible firearm butt-stock assembly claimed in claim 5, wherein said actuator is configured to cause said first and second locking members to move in opposite directions when said actuator moves in said second direction.
 7. The collapsible firearm butt-stock assembly claimed in claim 5, wherein said first guide rod is provided with a plurality of said first guide rod recesses and said second guide rod is provided with a plurality of said second guide rod recesses and each said first guide rod recess is disposed opposite and facing a said second guide rod recess.
 8. The collapsible firearm butt-stock assembly claimed in claim 1, wherein said actuator is provided with recessing to receive said at least one locking member when said actuator is moved in said first direction.
 9. The collapsible firearm butt-stock assembly claimed in claim 1, wherein said at least one locking member comprises at least one rolling element.
 10. The collapsible firearm butt-stock assembly claimed in claim 1, wherein said actuator is provided with at least one inclined face that faces said shoulder stock and is configured to drive said at least one locking member in a radially outwards direction when said actuator moves in said second direction.
 11. The collapsible firearm butt-stock assembly claimed in claim 1, wherein said actuator moves parallel to said first and second guide rods when moving in said first and second directions.
 12. The collapsible firearm butt-stock assembly claimed in claim 1, wherein said housing is provided with a buffer tube through-hole configured to house a buffer tube.
 13. The collapsible firearm butt-stock assembly claimed in claim 9, wherein said shoulder stock comprises a hole aligned with said buffer tube through-hole and configured to receive a buffer tube housed in said buffer tube through-hole at least when said shoulder stock is in a position corresponding to a fully collapsed condition of the collapsible firearm assembly.
 14. A collapsible firearm butt-stock assembly comprising: a buffer tube housing having a hole to receive a buffer tube; a first guide rod and a second guide rod; a shoulder stock coupled to said guide rods; and a locking mechanism for locking said shoulder stock in at least one fixed position relative to said buffer tube housing; wherein said buffer tube housing is provided with respective guide holes that are configured so that said guide rods can slide in said guide holes to permit movement of said shoulder stock relative to said buffer tube housing such that the shoulder stock can be moved towards and away from said buffer tube housing in a lengthways direction of said buffer tube housing, wherein said guide rods each have a plurality of guide rod recesses disposed at spaced apart locations along said guide rods to define respective extended positions of said shoulder stock, wherein said locking mechanism comprises a first locking member that is releasably engageable with the guide rod recesses of said first guide rod, a second locking member that is releasably engageable with the guide rod recesses of said second guide rod and a user operated actuator operable to release said first and second locking members from engagement with said guide rod recesses, and wherein said actuator is configured to be movable by a said user in a direction parallel to the lengthways direction of said first and second guide rods to release said first and second locking members from engagement with said recesses.
 15. A firearm comprising a collapsible firearm butt-stock assembly, wherein said collapsible firearm butt-stock assembly comprises: a housing provided with a first guide hole and a second guide hole; a shoulder stock coupled to a first guide rod that is inserted in said first guide hole and a second guide rod that is inserted in said second guide hole, the guides rods being configured so as to be able to slide in the respective guide holes to allow movement of said shoulder stock relative to said housing; and a locking mechanism comprising at least one locking member releasably engageable with at least one guide rod recess defined by said guide rods to limit said movement of the shoulder stock relative to said housing, and a user operable actuator that is movable in i) a first direction that is away from said shoulder stock to release said at least one locking member from engagement with said at least one guide rod recess to allow said guide rods to slide in said guide holes so that said shoulder stock can move relative to said housing and ii) a second direction that is towards said shoulder stock to cause said at least one locking member to engage said at least one guide rod recess.
 16. The firearm claimed in claim 15, wherein said firearm is of the AR15/M16/M4 series of firearms.
 17. A method of adjusting a collapsed/extended state of a collapsible firearm butt-stock assembly that comprises a shoulder stock coupled to a first guide rod and a second guide rod that are inserted in respective guide holes that are provided with a housing fixed to the firearm and a locking mechanism that has respective locking members that releasably engage respective guide rod recesses defined by said first and second guide rods, the method comprising: moving an actuator at least partially housed in said housing in a first direction that is away from said shoulder stock and into said housing to cause said locking members to disengage from said guide rod recesses to permit movement of said shoulder stock with respect to said housing.
 18. The method claimed in claim 17, further comprising using a hand to grip a pistol grip of said firearm and moving said actuator in said first direction with a thumb of said hand.
 19. The method claimed in claim 18, wherein a trigger finger of said hand is inserted in a trigger guard of said firearm.
 20. The method claimed in claim 17, wherein said actuator is moved parallel to said first and second guide rods when moving in said first direction. 